1. Field of the Invention
The present invention relates to pipe connectors, and more particularly to snap lock connectors for use with oil well casing and conductor pipe.
2. Description of Prior Art
When a well is drilled into the earth, as for the production of oil and gas, a large diameter pipe, known as surface casing, is usually installed in the upper section of the borehole. Surface casing stabilizes the walls of the borehole near the surface where they are more apt to cave in. On wells drilled in offshore waters from platforms or jack-up rigs, the pipe further extends from the ocean floor to the deck of the rig and is known as a marine riser. In such case, the riser is an extension of the surface casing. Pipe of this type usually ranges from 20 inches in outside diameter (O.D.) to 42 inches O.D. Some special applications use larger diameter pipe. Casing is usually installed in the ground to depths ranging from 50 to over 1,000 feet, and due to handling requirements is usually provided in lengths of from 30 to 50 feet.
During installation these pipe sections, or joints, must be connected together to provide structural integrity and to prevent leakage of fluids. This can be accomplished either by welding or by a disengagable mechanical type connector. Of these two general methods the mechanical connector is preferred since it requires less time to make a connection. This saves a considerable amount of money since rigs are usually leased on a daily rate. Saving rig time is particularly important offshore where rig rates are much higher than for equivalent land rigs.
Mechanical type connectors are available generally in two types. The first is the screw type in which an externally-threaded end, known as a pin, mates with an internally-threaded section known as a box. The second is the snap-lock type without threads in which the pin is simply pushed into the box where it is secured by a latching mechanism. The latter type is usually preferred for the large, low pressure surface casing string since it is both easier and faster to "stab" the pin into the box than to screw the two sections together.
Snap-lock connectors currently available use a snap ring, which is generally fabricated using spring material and has a gap to permit expansion and contraction. The snap ring is usually disposed in a recess either in the pin or the box, and the other connector has a groove directly opposite therefrom when the two connector ends are fully engaged. When the pin is inserted in the box carrying the snap ring, the snap ring is expanded by a tapering section on the pin until the mating grooves are opposite each other. At that point the expanded ring relaxes and snaps into engagement with the mating groove in the pin. With the ring mounted on the pin, the box causes the ring to contract until the ring can relax and expand into engagement with a groove in the box. The ring bridges the box and pin together and prevents them from disengaging until external actuating forces are placed on the ring and it is either expanded or contracted as appropriate.
Accordingly, it is an object of the present invention to provide a new and improved casing connector for the uses as previously described.
It is another object of the present invention to provide a new and improved type connector for casing, or the like, having increased structural strength. A connector must be strong enough to prevent failure under heavy load or flexture, as when a casing string is buffeted by wave action while being run from a floating vessel.
Another object of the present invention is to provide a pipe connector having pressure integrity to prevent environmental pollution and to prevent loss of costly drilling fluids.
A further object of the invention is to provide a pipe connector having easy stabbing characteristics, which is to say that it must be easy to align two adjacent sections of pipe, or casing, and to insert the pin connector into the box connector. Otherwise considerable time can be lost attempting to maneuver large heavy sections of casing into alignment and connection, particularly on offshore floating rigs where wave action can severely exacerbate the problem.
Yet another object of the invention is to provide a pipe connector having a mechanism for securing two sections of pipe together that operates quickly. This is important in achieving the aforementioned goal of saving valuable rig time.
Still another object of the invention is to provide a pipe connector having a compact locking mechanism without sacrificing either structural strength or gripping capacity. Conventional locking rings require wide cross sections to provide both requisite structural strength and gripping capacity, thereby requiring excessively large and costly joints.
Other objects and advantages of the invention will become apparent from a reading of the attached claims and description of the preferred embodiments.